On April 2nd, 2011, a team of perplexed students, gardeners, and community members gathered with shovels and rakes in hand at the base of Wellesley College’s observatory telescopes pondering the forest of purple, orange, and green stakes poking up from a snow-covered meadow. Mother Nature pulled an April Fools prank of dumping 3” of snow on the site of the Edible Ecosystem Teaching Garden (EETG) for the first morning of our weekend-long implementation workshop. This did not chill the spirits of those who had come to help Kristina Jones, director of the College’s Botanic Gardens, and our design team, as we began planting this experiment in applied ecology. We shoveled snow, grubbed, and sheet mulched patches outlined by wooden stakes, and explained that each bed was designed as a food-producing, low-maintenance analog of natural ecosystems. By the end of the weekend, we had nearly completed planting the 9,300 square foot Nut Grove, first of the eight habitats within the EETG.

After one year, plants overtake woodchips in the Wellesley’s Edible Ecosystem Teaching Garden.

This spring, during a hot, sunny workday with the some of the Wellesley College Botanical Garden’s summer interns, we were pleased to see that the vast seas of woodchips which dominated the character of the Garden even last fall are now carpeted in a mantle of nutrient accumulating, beneficial insect attracting, colorful, and tasty herbaceous perennials punctuated by small but healthy woody plants. But, alas, not all has gone as planned. Expansive opportunistic species that we sought to suppress have found chinks in sheet mulch while some promising species we planted did not survive the winter. As we move into Year Two of a 5-7 year establishment plan, we’d like to share the harvest of learning that EETG’s polycultures have yielded since our first slushy implementation day.

Managing Competition and Directing Succession

The spirit of this project, the qualities of the site, and the available resources made setting the successional clock back to zero using conventional disturbance techniques such as herbicide or tillage both impractical and undesirable. However the dominance of several expansive species like crown vetch, various brambles, spurge, and quack grass within the existing plant community would likely limit the ultimate diversity of useful groundcovers in the designed communities. Therefore we are trialing several techniques to manage succession as we nudge this former meadow toward a diversity of horizon habitats. Each technique, including Instant Succession, Nuclei that Merge, and Insertion Plantings, is intended to minimize long-term maintenance requirements while maximizing the garden’s performance.

Instant succession involves simultaneously planting the species intended to dominate the habitat at the successional horizon (say, 50 years from now), as well as all the plants intended to dominate in earlier stages of succession. The idea is to plant them all at once, and then “just add water”—an instant succession! Ideally, succession would then simply proceed apace, resulting in the proposed horizon habitat in about the number of years one intended. One large bed at the eastern edge of the Nut Grove exemplifies this approach. This bed now contains young shrubs and trees that will come to dominate the overstory of this future nut and fruit thicket. However, since the woodies are small, the bed is now dominated by sun-loving herbaceous species. We intend these plants to cover the ground, outcompete weeds, improve the soil, attract beneficial organisms, reduce herbivory of the woodies by deer until the woodies are well established, and provide some food, while requiring minimal care ONCE ESTABLISHED!

Polyculture action: Chives and dwarf comfrey blossoms attract beneficial insects and can confuse predatory herbivores with their strong scent. Astragalus acts as vigorous groundcover while also fixing nitrogen. Over time, the ‘main crop’ plants like Jostaberry (far left) will come to dominate these patches.

We have used the Nuclei that Merge technique to establish the majority of woody plants in the Nut Grove. Since the nut grove is so large and our budget and labor force are relatively small, we avoid disturbing large areas of soil that would require weeding and erosion control. The Nuclei that Merge strategy involves disturbing a small circular patch (size depends upon the weediness of the existing species at each planting location), planting a single tree or shrub in the center of the circle, sheet mulching the disturbed zone with cardboard and wood chips, and then planting groundcover polycultures through the sheet mulch. We intended to surround each disturbed circle with a 4-foot wide black plastic mulch “donut” to kill weeds and prepare the space for the nucleus of groundcovers to expand, but we did not do this the first year due to labor and budget limitations.

Mulch donuts (20-year weed barrier) protect nuclei-that-merge plantings like this Hazelnut, mint, astragalus, and barren strawberry polyculture from weed intrusion during establishment. Later, when the nucleus is strong, the plastic mulch will be removed and the weed-free space planted in useful ground covers (5/30/12).

A perspective shot of the nuclei-that-merge reveals the pattern of the plantings.

Insertion Plantings was the name we gave to species planted in areas where the existing plant community was dominated by desirable species, like a large patch of low-bush (V. angustifolium) and hillside blueberries (V. palladium), and we sought to diversify the patch yields with a minimum of disturbance. The four species planted in this manner (Senguin chestnut, Chinkapin hybrid, European filbert, and American Plum) are growing acceptably but may have benefited from fertility supplements.

Performance of Species and Polycultures

In natural communities, interspecies interaction can be mutually beneficial, like the relationship between some fungi and plant roots in the form of mycorrhizae. Among the many ideas embodied in the EETG is an attempt to design mixed patches of herbaceous and woody plants that maximize positive interactions while minimizing competition and predation. Within these experimental polycultures we expected to see some plants acting as nurse species by providing nutrients and minimizing ‘weed pressure’. Other plants might support heavier yields by attracting pollinators, while still others might hide long-term crop plants like hazelnuts from herbivores and other pests.

During our spring visit it was very satisfying to sit and watch the bees, wasps, and flies foraging among the chives and yarrow which have done a banner job of taking and holding ground, and attracting these early beneficial insects.

Astragalus glycyphyllos looks to be a great ground cover polyculture component, though it is a challenge to distinguish it from our main herbaceous rival, crown vetch. The mixture of clumpers, runners, and mat-formers seems to be working well as a ground cover strategy, and is adapting to the loss of a few species that have yet to come into their own (Waldsteinia fargarioides) or may die out completely (Rubus ‘Betty Ashburner’).

Chives dominate this experimental polyculture surrounding a Josta Berry tree. Note the permanent tag in the foreground. A QR code in the bottom right allows student, faculty, and visitors to easily collect data or just to learn more about the polyculture using a custom smartphone app developed at Wellesley. The app will be available on i-tunes later this summer.

While we observed significant signs of herbivory among woody species planted with less dense polycultures, specimens surrounded by tall, aromatic herbs appeared to have much less damage. We are inclined to surmise (or hope) that these herbs are protecting/hiding these woodies from herbivory and that these woodies will emerge from the herbaceous understory stronger and better able to respond to future browsing.

Performance of Implementation Strategies

Overall, the 2011 plantings seem to be thriving and we are pleased with the performance of the various implementation strategies being trialed on-site. Of course, we’ve also had to adapt our thinking/management in some areas. Below are some observations we’ve made about specific strategies and techniques.

Weed Suppression: We have reconfirmed our belief that for weed suppression, it is optimal to sheet mulch in the spring or early summer, not the fall. Deep wood chip mulch can suppress weeds for one growing season perhaps, but not for much longer, especially given crown vetch and woody vines like Virginia creeper and bittersweet.

In one area slated to have an especially intricate, diverse herb layer, we trialed a combination cardboard and coconut fiber sheet mulch. We have strong evidence that our original sheet mulch strategy for the difficult-to-control crown vetch would have worked well if it had been implemented properly by the contractor. Two shingled layers of cardboard covered in coconut fiber erosion control mat would likely persist for two growing seasons. Because the coconut fiber mat allows the cardboard to dry out, it seems also to allow the cardboard to maintain its integrity long enough to be able to effectively control long-lived herbaceous competitor species. The mat also holds the cardboard down and makes it look pretty decent, actually, while still being able to be mulched over at planting time. Eventually it decays into organic material to feed the soil. Replacing the coconut fiber mat with jute would cost much less, but it is very difficult to find jute that is not treated with kerosene.

We found cardboard and deep mulch provided the best weed barrier when applied in the spring, not the fall.

Our Nuclei that Merge/Expanding Mulch Donuts strategy would have worked better if we had installed the encircling black plastic mulch kill strips at planting time, much to our chagrin. Having not done this, we had more weed creeping in from the edges of the nuclei that demanded more work from our volunteer crews. Had we laid the plastic donuts before sheet mulching, we would have had a tight perimeter of defense against such creepers in year one and less labor would have been necessary last year, and probably this year as well.

With good sheet mulch technique and intensive planting, weed control can take the form of intensive pulses a few times in the growing season. Once ground covers are well established, it will diminish further, though the challenge of finding weeds and eliminating them from a complex polyculture will call forth better pattern recognition and creative removal techniques. We still have much to learn! And that is the point of the garden anyway—to research while we eat our way across the landscape.

Plant Densely, Invest in Soil Fertility: In addition to sheet mulching , completely occupying available niches and growing space with desired species, was one of the key implementation strategies deployed at the EETG. We intended that by this time most of the ground cover plants would have filled in the spaces between them for complete ground cover and weed suppression. In the Instant Succession bed we have nearly achieved this goal, with approximately 85% coverage. While we expect the Instant Succession bed will complete that process by midsummer, we have a few problem areas. Budget and plant availability limitations prevented us from planting quite as intensively as we had hoped, leading to more available space for weeds to break through and compete. This has led to the need to weed several beds regularly, but after midsummer, the labor requirement for weeding in most of the area planted in spring 2011 should diminish radically. We’ve also observed that areas without compost additions are not performing as well as those that received compost supplements.

Fulfilling a Vision and Promise

After only one year, the EETG already feels like the fulfillment of a vision and a promise, but much remains to implement, to learn, and to appreciate. It is the interaction of unique elements that makes the system a whole functioning ecosystem—and we can already see that taking shape at WCBG EETG. We look forward to seeing how the dynamics change as time goes on, and hope we can discover better ways to create functioning polycultures and ecosystems.

One Year’s Growth: The most dramatic transformation occurred in the instant succession bed. In just over one calendar year, sheet mulching (pictured in progress at left, 4/2/11) and dense plantings of multi-functional herbaceous plants like chives (in flower at right 5/30/12), yarrow, Astragalus, and Coreopsis transformed this old field into a diverse, food producing garden.

Dave Jacke, Dynamics Ecological Design, has been a student of ecology and design since the 1970s, and has run his own ecological design firm since 1984. He holds a B.A. in Environmental Studies from Simon’s Rock College and a M.A. in Landscape Design from the Conway School of Landscape Design. He is the author of the two-volume book, Edible Forest Gardens, the definitive reference text in this new area of horticulture.

Keith Zaltzberg, Regenerative Design Group, is an ecological designer who draws on his experiences as an instructor and organic farmer to create beautiful, vital and productive landscapes. Keith holds a B.S. in Environmental Design from the Department of Landscape Architecture and Regional Planning at the University of Massachusetts – Amherst.

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